There are known from German Offenlegungsschrift No. 3405611 antitumor active compounds. Thereby there are described (1,2-diphenyl-ethylenediamine)-platinum (II) complex compounds of the general formula ##STR2## wherein the groups R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are the same or different and are hydrogen, hydroxy groups, C.sub.1 -C.sub.6 -alkoxy groups, C.sub.2 -C.sub.6 -alkanoyl groups, optionally substituted by halogen atoms or C.sub.1 -C.sub.4 -alkanesulfonyloxy groups, or C.sub.3 -C.sub.6 -alkenoyloxy groups, wherein at least one of the groups R.sub.1, R.sub.2, R.sub.3, or R.sub.4 is not a hydrogen atom and x is the equivalent of a physiologically compatible anion.